Sanket Patil G^1*, Sharanabasavaraj Devareddy²

¹Senior Resident, Department of General Medicine, SIMSAR, BEML Nagar, KGF-563115 INDIA.

²Senior Resident, Department of General Medicine, Meenakshi Medical College, Kancheepuram, Tamil Nadu, INDIA.

Email: sanketpatilg07071989@gmail.com, sharanureddy92@gmail.com

Table 1: Table Showing Base Line Characteristics Of 100 Patients

Table 2: Distribution of patients according to hyponatremia on admission and at 72 hours and outcome in terms of mortality

Table 3: Comparison of severity of Hyponatremia and outcome in terms of mortality

Number of patients with sodium levels less than 130 is 7 and mortality was 4(57.14%). Number of patients with sodium levels between 131-134 is 25 and mortality was 4(16.11%).

Table 4: Comparison of Survivors and non survivors for various factors

Table 5: Multivariate analysis of sodium levels in MI patient

It was seen that serum sodium levels was statistically significant in determining mortality. Mean serum sodium level was 136.96 ±4.02 in the survivors and 131.63±4.24 in nonsurvivors. Other factors such as Killip class, hypertension, diabetes, age and sex were found to be statistically significant in determining mortality. Multivariate analysis using logistic regression analysis was performed (table 5) including variables that had p value < 0.2 in the univariate analysis to identify the variables that were independently associated with 30 day mortality. Multivariate analysis showed that along with other risk factors, hyponatremia was the significant independent predictor of 30 day mortality.

DISCUSSION

Our study suggests that patients presenting with acute myocardial infarction who had hyponatremaia on admission or developed hyponatremia after admission represent high risk population. In our study substantial proportion of patients who presented with acute ST elevation myocardial infarction were hyponatremic on admission or developed hyponatremia shortly after admission. In our study, hyponatremia was present on admission in 29 patients (29%). Hyponatremia developed in 13 patients(13%) during the first 72 hours of hospitalisation. In a similar study conducted by Goldberg18 et al, hyponatremia was present in 131 patients (12.5%) and hyponatremia developed in 208(19.9%) during the first 72 hours of hospitalisation. Patients who presented or developed hyponatremia more often had diabetes, anterior infarction and higher Killip class and lower ejection fraction. This is in accordance to the study conducted by Goldberg18 et al. In study done by Goldberg18 et al, a total of 105 deaths (10%) occurred within30 days of admission. 6.2% (44/708) of patients without hyponatremia, 19. 8% (26/131) of patients with hyponatremia on admission and 16.8% (35/208) of patients who developed hyponatremia after admission. Klopotowski et al, in their study of 1858 ST-elevation MI patients concluded that hyponatremia independently correlated with in-hospital mortality. Hyponatremics had higher rates of in-hospital mortality (13.5% vs 3.8%,p<0.001) composite of death and heart failure(27.8% vs 18.4%p=0.022).19

Ahmad Sajadieh et al in their study of 671 men and women aged 55 to 75 years with no history of cardiovascular disease, stroke, or cancer, found an adverse outcome defined as death or Myocardial Infarction(MI) occurred in 43% of patients whose serum sodium level was less than 134mEq/L. They concluded that Hyponatremia is an independent predictor of death and myocardial infarction in middle-aged and elderlypatients.²⁰ Bae et al reported that in hospitalized survivors of acute myocardial infarction, the presence of hyponatremia at discharge was an independent predictor of 12-month mortality. The study involved 1290 patients²¹ In comparision with the above study, our study had higher mortality in patients with hyponatremia on admission whereas mortality was almost equal in patients who developed hyponatremia after admission. In our study, odd‘s ratio for 30 day moratality in patients with hyponatremia on admission and patients who developed hyponatremia was high (3.143 and 12.0).This was in concordance with study done by Golderg18 et al. In our study, we found a trend of increasing mortality with the severity of hyponatremia. We stratified patients into two groups depending on the mean sodium level. The group with sodium level <130 mmol/L had 58% mortality and those with serum sodium in the range of 131-134mmol/L suffered 17% deaths. This was inconcordance with the study conducted by Goldberg18et al, who showed increasing mortality with severity of hyponatremia. When we compared the various risk factors and outcomes among the survivors and the non survivors, we found, apart from age, sex, diabetes, hypertension, Killip class on admission, ejection fraction, hyponatremia was significant risk factor in determining mortality. All the variables among the survivors and non survivors that were significantly associated with mortality were included in the multivariate logistic regression analysis. Hyponatremia remained a significant independent predictor of mortality. This is in concordance to similar study conducted by Goldberg18 et al. they found that hyponatremia was independently associated with 30 day mortality. In a similar study of 235 patients admitted to a coronary care unit, Flear et al., found higher in hospital mortality rates among patients with minimal plasma soidum levels ≤130mmol/L. Sigurdsson A, Held P, Swedberg K in their study of 55 patients with acute myocardial infarction concluded that sustained neurohormonal activation after myocardial infarction mainly occurs in patients with clinical heart failure and is related to the magnitude of myocardial damage, even in patients without heart failure.²² Tang et al also documented in their study that hyponatremia was independently associated with in hospital death and heart failure. Thus, Goldberg83 et al., concluded in their study that the development of hyponatremia is a marker that most likely incorporates different prognostic entities, including the severity of the left ventricular dysfunction, hemodynamic alterations and the extent of neurohumoralactivation.²³ It was observed that the development of hyponatremia is a biochemical marker for prognostic importance i.e. left ventricular dysfunction severity, hemodynamical changes and neurohumoral activation. Hence in our study, we concluded that hyponatremia on admission or early development of hyponatremia in patients with acute ST elevation MI is an independent predictor of 30 day mortality.

CONCLUSION

Hyponatremia on admission or early development of hyponatremia in patients with acute ST elevation myocardial infarction is an independent predictor of 30-day mortality. Plasma sodium levels may serve as a simple marker to identify patients atrisk.

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